Folded antennas for implantable medical devices

ABSTRACT

In an example, an apparatus can include an implantable medical device comprising a housing, an implantable telemetry circuit carried within the housing, a dielectric compartment mechanically coupled to the housing, the dielectric compartment including first and second substantially parallel face portions and a third face portion extending between the first and second face portions, and an implantable telemetry antenna, located at least partially within the dielectric compartment. The implantable telemetry circuit can be electrically coupled to the implantable telemetry antenna and configured to wirelessly transfer information electromagnetically using the implantable telemetry antenna. In an example the implantable telemetry antenna comprises a spiral conductor portion extending along the first, second, and third face portions. In an example the spiral conductor includes a cross section having a lateral width that can be greater than a sidewall height of the cross section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/302,202, entitled “Folded Antennas for Implantable Medical Devices,”filed on Nov. 22, 2011, now issued as U.S. Pat. No. 8,761,896, which ishereby incorporated by reference herein in its entirety.

This application claims benefit of priority under 35 U.S.C. 119(e) to:

1. Vajha et al., U.S. Provisional Patent Application Ser. No.61/416,655, entitled “Folded Antennas for Implantable Medical Devices”,filed on Nov. 23, 2010, which is hereby incorporated herein by referencein its entirety;

2. Vajha et al., U.S. Provisional Patent Application Ser. No.61/416,665, entitled “Folded Antennas for Implantable Medical Devices”,filed on Nov. 23, 2010, which is hereby incorporated herein by referencein its entirety; and

3. Vajha et al., U.S. Provisional Patent Application Ser. No. 61/416,663entitled “Modular Antenna for Implantable Medical Device”, filed on Nov.23, 2010, which is hereby incorporated herein by reference in itsentirety.

BACKGROUND

Implantable medical devices (IMDs) can perform a variety of diagnosticor therapeutic functions. In an example, an IMD can include one or morecardiac function management features, such as to monitor the heart or toprovide electrical stimulation to a heart or to the nervous system, suchas to diagnose or treat a subject, such as one or more electrical ormechanical abnormalities of the heart. Examples of IMDs can includepacers, automatic implantable cardioverter-defibrillators (ICDs),cardiac resynchronization therapy (CRT) devices, implantable monitors,neuromodulation devices (e.g., deep brain stimulators, or other neuralstimulators), cochlear implants, or drug pumps, among other examples.

Such IMDs can include electronic circuitry configured to wirelesslytransfer information between implanted IMDs, or between an IMD and anassembly external to the body. Such information can include, forexample, programming instructions or configuration information toconfigure the IMD to monitor, diagnose, or treat a physiologiccondition. Such information can also include data sensed, detected, orprocessed by the IMD and transmitted to another device or assembly(e.g., physiologic information, a disease status, etc.) An IMD caninclude an antenna sized and shaped to wirelessly transfer information,such as using a desired operating frequency range. Such a frequencyrange can be specified by a spectrum allocation authority within thecountry where the IMD may be located or used. Thus, the IMD generallyincludes an antenna tailored to the spectrum allocation regulationswhere the IMD may be used or sold.

OVERVIEW

Generally, active implantable medical devices (IMDs) can include apacemaker, a defibrillator, a cardiac resynchronization therapy device,a neurostimulation device, an implantable monitoring device, or one ormore other devices. Information can be wirelessly transmitted to, orreceived from, such IMDs, such as using electromagnetic waves. Suchelectromagnetic waves can be transmitted or received using animplantable antenna included as a portion of the IMD. Suchelectromagnetic transmission can provide an effective communicationrange on the order of meters, as compared using a communication schemeinvolving mutual-inductive magnetic coupling. Such magnetic coupling isgenerally limited to an effective communication range of onlycentimeters.

In Zart et al. (U.S. Pat. No. 7,309,262), a connector assembly for animplantable medical device is mentioned. The connector assembly includesa core element formed of a thermoplastic material, and a circuit memberincluding an antenna structure extending over a portion of the coreelement outer surface.

In Abadia et al., “3D-Spiral Small Antenna Design and Realization forBiomedical Telemetry in the MICS band,” Radioengineering, vol. 18, no.4, (December 2009), pp. 359-367, a dielectric-loaded antenna including acoaxial feed, a ground plane, and a grounding pin between a metal patchportion of the antenna and the ground plane are provided.

In Kwak, “Ultra-wide band Spiral shaped small Antenna for the BiomedicalTelemetry,” APMC2005 Proceedings, Institute for Electrical andElectronics Engineers (2005), a coaxially-fed spiral antenna forbiomedical telemetry is mentioned. The antenna includes a flat conductoron a dielectric material, above a ground plane, in an air-filledcapsule.

After an IMD is implanted, it is generally surrounded by various bodilytissues or fluids. Such tissues or fluids (e.g., muscle tissue, fattytissue, bone, blood, etc.) are somewhat conductive (e.g., lossy),inhomogeneous (e.g., having a varying loss and dielectric permittivity),and can have a relatively high dielectric permittivity as compared tofree space. Because the medium surrounding the IMD in vivo can vary, andis different than a free space environment, the implantable antennaincluded as a portion of the IMD can be located at least partiallywithin a dielectric compartment. Such a dielectric compartment canprotect the implantable antenna from exposure to tissue or bodily fluidsthat may degrade antenna performance. Also, the dielectric compartmentcan improve operating consistency of the implantable antenna (e.g., ausable range, a directivity, a gain, or other performance) for both afree-space use environment before implant, and an in vivo environmentafter implant.

The present inventors have recognized, among other things, that thetotal volume of space occupied by an IMD can be an importantconsideration to both implanting physicians and patients. Thus, the sizeand shape of a dielectric compartment including the implantable antennacan be determined in part by spatial constraints (e.g., an allowablevolume or surface area), and by biocompatibility considerations (e.g., amaterial or a shape can be selected to be compatible with, andunobtrusive to, the patient), rather than just electrical performanceconsiderations. However, antenna length and volume are still generallygoverned by electrical performance needs as well. Generally, an antennalength, such as for a monopole antenna, can be about an odd-multiple ofa quarter of a wavelength in a specified medium (e.g., ¼ of awavelength, ¾ of a wavelength, etc.), corresponding to a desiredresonant operating frequency within a desired operating frequency range.

As the desired operating frequency range decreases in frequency, thelength and volume occupied by a relatively straight quarter-wavelengthmonopole (or half-wavelength dipole antenna) can become undesirablylarge, despite the higher relative dielectric permittivity of a tissueenvironment. For example, in some countries, wireless transfer ofinformation can use a first specified range of frequencies around 900megahertz (MHz), or some other range of frequencies, such as specifiedby a spectrum allocation authority. However, in other countries, or atthe preference of a health care provider or caregiver, a secondspecified range of frequencies around 400 MHz may be used instead of, orin addition to, the first specified range of frequencies. The presentinventors have recognized, among other things, that the total length ofan antenna designed to work at around 900 MHz may need to more thandouble in order for such an antenna to be used at around 400 MHz. Such adoubling in length may be unacceptable to end users because such adoubling in length may unacceptably increase the volume or area used bythe implantable antenna.

Accordingly, the present inventors have also recognized that theimplantable antenna can be made more compact than a straight monopole orstraight dipole antenna, such as by using a more complex antenna shape,while still meeting design goals that constrain a total antenna volumeor area. Moreover, the present inventors have also recognized that sucha compact antenna, such as including one or more of a spiral conductor(e.g., a conductive material arranged in a spiral pattern), or anothershape (e.g., a serpentine conductor shape), can still have a physicalpath length approaching a quarter wavelength (or a half wavelength inthe case of a dipole antenna). In an example, an implantable antennaincluding a spiral conductor can provide electrical performancecomparable to a straight monopole (or dipole) conductor.

In an example, such a spiral conductor or other shape, such as aserpentine conductor shape, can be fabricated in a substantially planarpattern (e.g., etched, stamped, or cut out of a sheet of material in arelatively flattened pattern, such as providing a conductive patternhaving a ribbon-shaped conductor cross section). Then, such a planarpattern can be formed or folded into a configuration to conform to, orextend along, one or more faces of the dielectric compartment. In anexample, such a dielectric compartment can include a header attached toan IMD, the header including one or more connectors to electrically ormechanically mate with one or more implantable leads.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 illustrates generally an example of an apparatus that can includean implantable medical device wirelessly coupled to an external module.

FIG. 2 illustrates generally an example of an apparatus that can includean implantable medical device, such as including an implantabletelemetry circuit coupled to an implantable antenna including a spiralconductor.

FIGS. 3A-B illustrate generally examples of an apparatus that caninclude an implantable antenna located at least partially within adielectric compartment.

FIGS. 4A-B illustrate generally examples of an apparatus, such as aportion of the apparatus of the examples of FIGS. 1-2, that can includea spiral conductor having a specified shape or configuration.

FIGS. 5A-C illustrate generally views of an example of at least aportion of an implantable antenna including a spiral conductor includinga cross section having a lateral width that is greater than a sidewallheight of the cross section, and having a specified separation betweenadjacent turns of the spiral conductor, and between the spiral conductorand another conductor.

FIGS. 6A-C illustrate generally views of an example of at least aportion of an implantable antenna, such as shown in the examples of FIG.1-2, 3A, 4A-B or 5A-C, such as including a first conductive segment anda second conductive segment mechanically and electrically coupled usinga specified transition portion.

FIGS. 7A-D illustrate generally a technique for fabricating a spiralconductor, such as shown in the examples of FIG. 1-2, 3A, 4A-B or 5A-C,such as including patterning or etching a planar conductor to provide aplanar spiral pattern, and folding or forming the planar spiral patterninto a specified configuration.

FIGS. 8A-C illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly.

FIG. 9 illustrates generally an example of an apparatus that can includean implantable antenna comprising a loading portion.

FIGS. 10A-B illustrate generally an example of an apparatus that caninclude an implantable antenna including a spiral conductor.

FIGS. 11-18 illustrate generally examples of an apparatus that caninclude an implantable antenna including a spiral conductor, the spiralconductor sized and shaped to provide specified electrical operatingcharacteristics within a specified operating frequency range, theexamples including various dielectric compartment and housingconfigurations.

FIGS. 19A-B, 20A-B, 21A-B illustrate generally examples of an apparatusthat can include an implantable antenna including a spiral conductor,the spiral conductor sized and shaped to provide specified electricaloperating characteristics within a specified operating frequency range,the examples including various dielectric compartment and housingconfigurations.

FIG. 22 illustrates generally an example of technique that can includeproviding an implantable medical device including an implantabletelemetry antenna, and wirelessly transferring informationelectromagnetically using the implantable telemetry antenna.

FIGS. 23A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly.

FIGS. 24A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly.

FIGS. 25A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly.

DETAILED DESCRIPTION

FIG. 1 illustrates generally an example of an apparatus 100 that caninclude an implantable medical device (IMD) 102, implanted within a body(e.g., a patient 101), such as wirelessly coupled to an external module115. In an example, the IMD 102 can include an implantable devicehousing 105, such as including a conductive portion (e.g., ahermetically-sealed titanium housing, or a housing including one or moreother materials). For example, the housing 105 can contain at least aportion of an implantable telemetry circuit 106, such as a transmitter,a receiver, or a transceiver, configured to wirelessly transferinformation electromagnetically using an implantable antenna 110 such asincluded at least partially within a dielectric compartment 107. In anexample, the external module 115 can include an external antenna 117coupled to an external telemetry circuit 116.

In an example, the external module can include a physician programmer, abedside monitor, or other relatively nearby assembly, such as used totransfer programming instructions or configuration information to theIMD 102, or the receive diagnostic information, a disease status,information about one or more physiologic parameters, or the like, fromthe IMD 102. The external module 115 can be communicatively connected toone or more other external assemblies, such as a remote externalassembly 175, located elsewhere (e.g., a server, a client terminal suchas a web-connected personal computer, a cellular base-station, oranother wirelessly-coupled or wired remote assembly). The implantableantenna 110 can include a spiral conductor, or one or more otherconductor shapes or configurations, such as shown and discussed in theexamples below.

FIG. 2 illustrates generally an example of an apparatus 200 that caninclude an IMD 202, such as including an implantable telemetry circuit206 coupled to an implantable antenna 210 including a spiral conductor209B. In the example of FIG. 2, the spiral conductor 209B can be fed bya conductive segment 209A. The conductive segment 209A can besubstantially perpendicular to a surface or face of a housing 205, suchas the housing 205 that comprises a conductive portion. For example, theconductive segment 209A can include a loading portion configured toadjust an input impedance of the implantable antenna 210, to provide aninput impedance within a specified input impedance range at a specifiedrange of frequencies. In an example, the conductive segment 209A can beused to reduce or eliminate a capacitive contribution to the inputimpedance of the implantable antenna 210, such as by reducing acapacitive interaction between the conductive segment 209A and thehousing 205.

In an example, at least a portion of the implantable antenna 210 can belocated at least partially on or within a dielectric compartment 207.For example, the dielectric compartment can include a biocompatiblematerial such as an epoxy, a thermoplastic polyurethane (e.g.,TECOTHANE™), or one or more other materials. In an example, thedielectric compartment can comprise a header including one or moreconnectors configured to mate with an implantable lead assembly, such asshown in the examples of FIG. 8-9, 10A-B, 11-18, 19A-B, 20A-B, or 21A-B.In an example, one or more of the spiral conductor 209B or theconductive segment 209A can include a ribbon shape or other crosssection, such as shown in the examples of FIG. 8-9, 10A-B, 11-18, 19A-B,20A-B, or 21A-B. In an example, the spiral conductor 209B can instead bereplaced by one or more other conductive shapes, such as the serpentineconductor of FIG. 3B.

FIGS. 3A-B illustrate generally examples of an apparatus, such as aportion of the apparatus of the examples of FIGS. 1-2, that can includean implantable antenna located at least partially within a dielectriccompartment 307. FIG. 3A depicts a hypothetical longitudinal axis 350and an axis 360 perpendicular to the longitudinal axis 350. In theexample of FIG. 3A, an antenna 310 including a spiral conductor can belocated at least partially within the dielectric compartment 307 (e.g.,a header, or another portion of an IMD, such as discussed in theexamples above or below). In the example of FIG. 3A, the spiralconductor 310 can be oriented to extend along a first face 308A, asecond face 308B, or a third face 304, of the dielectric compartment307. For example, the first and second faces 308A-B can be substantiallyparallel (e.g., the sidewalls of the dielectric compartment 307). In anexample, a third face 304 can extend between the first and second faces308A-B, such as shown in FIG. 3A. In an example, the various faces ofthe dielectric compartment 307 need not be perfectly planar. In anexample, the dielectric compartment 307 can be formed by one or moremolding steps, such as using a thermosetting or a thermoplasticdielectric material.

In an example, unlike a helical or conical antenna, the spiral conductor310 can include multiple “turns” in a plane perpendicular to ahypothetical axis. For example, for a portion of the spiral conductor310 extending along the first face 308A, the turns of the spiralconductor can be “wound” concentrically in a plane substantiallyparallel to the first face 308A, along a hypothetical longitudinal axis350. In an example, such as in FIG. 3A, each “turn” need not becircular. For example, for a portion of the spiral conductor 310extending along the second face 308B, the turns can be again “wound” ina plane substantially parallel to the second face 308B, along thehypothetical longitudinal axis 350. In the example of FIG. 3A (and assimilarly shown in the examples of FIGS. 7A-D), the planar spiralpattern can be folded to extend along more than one face of thedielectric compartment 307, such as to place the implantable antenna 310at a specified depth from one or more of the first or second faces308A-B, or the third face 304.

In the example of FIG. 3B, a serpentine antenna 312 can be similarlylocated on or within the dielectric compartment 307, such as including afirst segment 313A extending along the first face, 308A, the second face308B, and the third face 304. In the example of FIG. 3B, unlike thespiral conductor example of FIG. 3A, the instantaneous direction of acurrent flowing through the serpentine antenna 312, such as at or nearresonance, can include a first direction (e.g., indicated by an arrow inFIG. 3B) associated with the first segment 313A. In such an example, theinstantaneous current flowing through a second segment 313B, or a thirdsegment 313C, can include a second, opposite, direction. In the exampleof FIG. 3B, the second and third segments 313B-C can extend along thelateral edges of the first segment 313A. However, if the first-thirdsegments 313A-C are about the same depth from an exterior face of thedielectric compartment 307, the net radiated electromagnetic field isreduced as compared to the example of FIG. 3A. The decrease in the netradiated field can be due in part to a cancellation effect from thefirst and second current directions. For example, the electromagneticfield generated by the current flowing in the first direction iscounteracted by the respective field contributions from the adjacentsegments having respective currents flowing in the second, opposite,direction.

The present inventors have also recognized that this cancellation effectcan be reduced somewhat by staggering the depths of the various segmentswith respect to an exterior face of the dielectric compartment 307. Forexample, in FIG. 3B, the first-third segments 313A-C are relativelyuniform in spacing from the first and second faces 308A-B. In anexample, the third segment 313 could be relatively further recessedwithin the dielectric compartment 307, as compared to the first andsecond segments 313A-B. Similarly, the first segment 313A could berecessed further into the dielectric compartment than the second segment313B, but not quite as far recessed as the third segment 313C. In anexample, staggering the depths of the first, second and third segments313A-C can also reduce unwanted coupling between adjacent segments(e.g., due to a fringing field effect). Such unwanted coupling cangenerally increases the capacitive portion of the input impedance of theantenna, and can at least partially “short out” the current flowing onthe antenna, reducing the antenna's effective length or radiationefficiency, for example.

FIGS. 4A-B illustrate generally examples of an apparatus, such as aportion of the apparatus of the examples of FIGS. 1-2, that can includea spiral conductor 410A-B having a specified shape or configuration. Inthe example of FIG. 4A, a spiral conductor (e.g., similar to the spiralconductors included as a portion of the antenna 110, 210, or 310 shownin the examples of FIGS. 1-2, 3A) can include a specified distancebetween adjacent turns, “d₁.” The spiral conductor 410A can also includea conductor having a specified lateral width, “w₁.” In the example ofFIG. 4A, the distance, “d₁,” can be relatively uniform (e.g., constant)along the path of the spiral conductor 410A. In FIG. 4A, the lateralwidth, “w₁,” can taper (or otherwise vary in a specified or controlledmanner) along the path of the spiral conductor 410A.

Similarly, FIG. 4B illustrates an example where a lateral width, “w₂,”can taper (or otherwise vary in specified or controlled manner), alongthe path of the spiral conductor 410B, while a distance, “d₂,” betweenadjacent turns of the spiral conductor 410B can be relatively uniform.Such a tapering in either lateral width, or separation distance, orboth, can be used at least in part to adjust or provide one or moredesired electrical performance characteristics of an antenna includingthe spiral conductor 410A. For example, such adjustment can be used toprovide a specified input impedance, a specified antenna gain, aspecified directivity, or a specified current distribution along theantenna, or the like.

FIGS. 5A-C illustrate generally views of an example of at least aportion of an implantable antenna 510 including a spiral conductor. Inthe example of FIG. 5A, the antenna 510 can be monopole-like, such asusing a conductive region 505 as a counterpoise (e.g., a reflector). Inan example, an implantable antenna can include a dipole antenna (oranother antenna type), such as using two (or more) similar spiralconductors each similar to the antenna 510 shown in FIGS. 5A-C. In sucha dipole example, a counterpoise such as the conductive region 505 neednot be included. The line labeled “5B” of FIG. 5A indicates a horizontalcross-section of antenna 510 that is shown in detail in FIG. 5B. Theline labeled “5C” of FIG. 5A indicates a vertical cross-section ofantenna 510 that is shown in detail in FIG. 5C.

The antenna 510 can include a cross section having a lateral width, “w,”such as shown in FIG. 5B with respect to a first segment 510A in a firstturn of the spiral conductor. In the examples of FIGS. 5A-C, the lateralwidth, “w,” can be greater than a sidewall height, “h,” of the crosssection, again shown with respect to the first segment 510A in FIG. 5B.A specified separation, “d,” can be used between adjacent turns of thespiral conductor, such as shown in FIG. 5B, between the first segment510A in the first turn, and a second segment 510B in a second turn ofthe spiral conductor.

The present inventors have recognized, among other things, that variousundesired effects such as current cancelation or fringing-field effectscan be reduced or eliminated using various techniques. Such techniquescan allow the spacing, “d,” to be reduced as compared to antennaslacking such features as shown in FIGS. 5A-C. Such a reduction inspacing, “d,” can provide an antenna 510 that is more compact (e.g.,volumetrically, or in surface area) than antennas lacking such featuresas shown in FIGS. 5A-C. For example, use of a spiral conductor geometryas shown in FIGS. 5A-C can reduce current cancelation versus using theserpentine geometry of FIG. 3B, because the instantaneous currents inadjacent segments (e.g., segments 510A-C) generally flow in the samedirection when the antenna is operating in a first resonant mode.

Another technique can include staggering adjacent segments or turns ofthe antenna 510 in depth, such as locating a third segment 510C in theregion 510D, such as to reduce an interaction between adjacent segmentsdue to a fringing field 599 (e.g., an electric field indicative ofcapacitive coupling between adjacent segments). While such amodification to the location of segment 510C can result in an antenna510 that is not perfectly planar, such an antenna is still substantiallyplanar, since the change in the position of the segment 510C to thelocation of the region 510D can be very small, such as represented by“o,” in comparison to the total surface area of the plane of the antenna510. For example, FIG. 5A can represent a view of a plane along ahypothetical axis 550 on which the antenna 510 is “wound.” Thedimension, “o.” can represent an offset in depth between adjacent“turns” of the antenna, along the hypothetical axis 550. In an example,the total depth of the antenna 510 along such a hypothetical axis 550can be at least an order of magnitude smaller than a diameter or alargest linear dimension, “I,” of the antenna 510.

Yet another technique can include using an antenna 510 includingribbon-shaped cross section, such as a rectangular cross section asshown in FIGS. 5A-C, or an otherwise non-circular cross section, insteadof using a wire or round cross section. The present inventors haverecognized, among other things, that the antenna 510 including spiralconductor using a ribbon cross section, as shown in FIGS. 5A-C, can bemade more compact than a corresponding helical antenna or wire antenna.For example, the fringing field 599 interaction between adjacentsegments can be reduced if the ribbon conductor is oriented so that thethinner sidewalls are adjacent to one another as compared to locatingthe “fat” lateral portions of width “w” facing one another.

The illustrative examples of FIGS. 9, 10A-B, 11-18, 19A-B, 20A-B, and21A-B generally show the interaction between various physical parameterssuch as including the dimensions “w,” “h,” “d,” and “s.” In anillustrative example, if the antenna 510 is to be used for wirelesstransfer of information electromagnetically at a specified range offrequencies around 400 MHz, then the width, “w,” can be from a range ofabout 34 mils (0.034 inches) to about 50 mils (0.050 inches), or someother width. Generally, the sidewall height, “h,” can be kept small forthe reasons discussed above, but the thickness should not be so smallthat surface roughness increases resistance undesirably. In anillustrative example, a ribbon thickness (e.g., sidewall height, “h”)can be larger than a “skin depth” of current at the desired operatingfrequency. At around 400 MHz, the skin depth is around 1 mil (0.001inches). Thus, in such an illustrative example at 400 MHz, a surfaceroughness of about 0.1 mil (0.0001 inches) or less can be specified.

In an illustrative example, the distance between adjacent turns of thespiral conductor, “d,” can be from about 15 mils (0.015 inches) to about20 mils (0.020 inches), or some other distance, such as for providingconsistent performance at a specified range of frequencies around 400MHz, in both free space (e.g., air) or in a variety of different tissuemedia. Though the antenna 510 can be made more compact using a closerspacing of adjacent turns, such a closer spacing can result in a higherquality factor, “Q,” corresponding to a reduced usable bandwidth ascompared to an antenna having a wider spacing between adjacent turns.

In the example of FIG. 5C, the antenna 510 can be oriented so that theshort sidewall of the spiral conductor is substantially parallel to thenearby conductive region 505. The conductive region 505 can be at“ground” potential for alternating current signals, thus a separation,“s,” between a segment 510E and the conductive region 505 can bemaintained, such as to avoid unwanted loading of the antenna 510 by theconductive region. Similar to the discussion above with respect toadjacent segments, orienting the segment 510E so that the short sidewallis adjacent to the conductive region 505 can allow a smaller separation,“s,” than if the antenna had a round (e.g., wire) cross section, or ifthe antenna segment 510E were rotated 90 degrees so that the widerportion were closest to the conductive region 505. Thus, an antenna 510can be “tucked” into a physically constrained area within a dielectriccompartment, such as at the rear portion of a header for an IMD, whilestill maintaining a specified offset distance between the antenna 510and adjacent conductive structures, such as a conductive housing of theIMD.

FIGS. 6A-C illustrate generally views of an example of at least aportion of an implantable antenna, such as shown in the examples of FIG.1-2, 3A-B, 4A-B or 5A-C, such as including a first conductive segmentand a second conductive segment mechanically and electrically coupledusing a specified transition portion.

The examples of FIGS. 1-2, 3A, and 4A-B illustrate generally that anantenna for an IMD can include a spiral conductor. However, the spiralconductor need not include bends, radii, or transition portions for eachturn that are the same for every turn, or for every junction betweenadjacent segments within a respective turn. In the example of FIG. 6A, afirst segment 696A, such as ribbon-shaped conductor, can transition intoa second segment 697A, such as using a 90-degree corner 698A. In theexample of FIG. 6B, a first segment 696B can transition into a secondsegment 697B, such as via a “clipped” corner 698B. In the example ofFIG. 6C, a first segment 696C can transition into a second segment 697C,such as using a radiused transition 698C. In an example, as operatingfrequency increases (e.g., an operating wavelength becomes shorter),power bundling or a concentration in current can occur if a sharp corner698A or a clipped corner 698B is included, such as shown respectively inFIGS. 6A-B. For example, to avoid an unwanted peak in current magnitude,such as in a first or outer-most turn of an implantable antennaincluding a spiral conductor, the radiused transition of FIG. 6C can beused. Conversely, in an example, to provide a higher current density forone or more interior turns toward the center of the spiral conductorpattern, a sharper transition can be used, such as shown in the examplesof FIG. 19A-B, 20A-B, or 21A-B. Such heightened current density on oneor more interior turns can enhance radiation efficiency, while avoidingsuch sharp or clipped corners 698A-B on outer turns can help prevent anunwanted increase in a resistive contribution to an input impedance ofthe antenna.

FIGS. 7A-D illustrate generally a technique for fabricating a spiralconductor, such as shown in the examples of FIG. 1-2, 3A, 4A-B or 5A-C,such as including patterning or etching a planar conductor to provide aplanar spiral pattern, and folding or forming the planar spiral patterninto a specified configuration. In FIG. 7A, a sheet of conductivematerial 701 can be provided (e.g., a sheet of metal stock, etc.). Suchmaterial 701 can include one or more of aluminum, steel, stainlesssteel, a biocompatible alloy (e.g., platinum-iridium or anothermaterial), or a shape-memory material (e.g., a nickel-titanium alloy orother material). In an example, one or more portions of an implantableantenna can be patterned, etched, cut, stamped, or otherwise formed fromthe sheet of conductive material 701, such as to provide a substantiallyplanar spiral conductor 702 as shown in FIG. 7B. In an example, such aconductor 702 can have a ribbon-shaped cross section, such as includinga lateral width of a segment determined by the shape of the pattern, andincluding a sidewall height of the segment determined by the thicknessof the sheet of stock 701.

In an example, the material 701 can be a conductive material cladding adielectric material. For example, the material 701 can include one ormore of copper, aluminum, gold, platinum, or one or more metals oralloys, such as cladding a flexible or rigid dielectric substrate. In anexample, the dielectric substrate can include one or more of apolyimide, polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE),polyether-ether-ketone (PEEK), a thermoplastic polyurethane, an epoxy, aglass-epoxy laminate, or one or more other flexible or rigid materials.In such a cladded example, the material 701 can be etched or patternedto provide a desired conductor geometry, similar to the conductor 702,such as fabricated using one or more processes or techniques generallyused for printed circuit board (PCB) or printed wiring board (PWB)manufacturing.

In an example, the conductor 702 can then be folded, bent, or otherwiseformed into a desired two- or three-dimensional configuration, such asfolded around a hypothetical axis 703, as shown in FIG. 7C, to providean implantable antenna 710 having a specified configuration. In theexample of FIG. 7D, the implantable antenna 710 can include a firstsubstantially planar portion 705, and a second substantially planarportion 704. One or more of the first or second portions 704-705 can beovermolded, attached, inserted, or otherwise coupled to a dielectricmaterial (e.g., a dielectric compartment included as a portion of anIMD), such that one or more of the first or second portions 704-705extends along or is substantially parallel to a face of the dielectricmaterial. In an example, the conductor 702 can be folded along more thanone axis, such as shown in the example of FIG. 8, and elsewhere. In anexample, one or more techniques similar to those shown in the examplesof FIGS. 7A-D can be used, but instead including a serpentine antennaconductor pattern, such as shown in the example of FIG. 3B.

FIGS. 8A-C illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly. In an example, an IMDcan include a first dielectric portion 807A, and a second dielectricportion 807B, and a dielectric compartment 807. The second dielectricportion 807B can include a header the IMD, such as configured forattachment to a conductive housing. For example, the header can provideone or more mechanical or electrical connections to one or moreimplantable lead assemblies, An implantable antenna including a spiralconductor 810 can be located in an otherwise unused portion of theheader.

In an example, the first dielectric portion 807A can be a dielectricshell, such as including an interior-facing surface sized and shaped toaccommodate the spiral conductor 810. For example, the first portion807A can include one or more cavities, slots, stakes, ridges or otherstructures such as to provide or maintain a desired spacing or geometryfor the spiral conductor 810, such as to avoid deforming the spiralconductor 810 in an unwanted manner during manufacturing.

In the example of FIG. 8A, the first dielectric portion 807A can beconfigured to have two substantially parallel interior faces (e.g.,vertical sidewalls), and a portion extending between the twosubstantially parallel interior faces (e.g., the rear portion), toprovide a “u”-shaped shell. In an example, the spiral conductor 810 canbe inserted into or otherwise attached to the interior-facing surface ofthe u-shaped first dielectric portion 807A, such as using an injection(e.g., insert molding process).

In an examples of FIGS. 8B-C, the combination of the spiral conductor810 and the first dielectric portion 807A can then be attached to adesired location on the second dielectric portion 807B (e.g., such asusing a medical adhesive including silicone, or using an overmoldingprocess, or one or more other techniques). For example, use of themodular assembly technique as shown in FIG. 8 can provide a desiredseparation between the spiral conductor 810 and a conductive housing 805of the IMD.

FIG. 9 illustrates generally an example of an apparatus 900 that caninclude an implantable antenna comprising a loading portion 910A, and aspiral conductor portion 910B, such as located within a dielectricmaterial 907. In an example, the dielectric compartment 907 can be aheader attached to an IMD housing, as discussed in the examples above,such as including a lead bore 970 configured to receive an implantablelead assembly. In the example of FIG. 9, the loading portion 910A caninclude a different conductor cross section than the spiral conductorportion 910B, such as to adjust an input impedance of the implantableantenna to achieve a specified input impedance range within a specifiedoperating frequency range. For example, the spiral conductor portion910B can provide an input impedance in both free space and in vivo thatincludes a relatively large capacitive component. The loading portion910A can be used, at least in part, to reduce such a capacitivecomponent of the input impedance. In an example, the loading portion910A can include one or more other conductor shapes or configurations,such as a coil, a helix, a conductive segment oriented vertically withrespect to the housing of the IMD, or one or more other conductorshapes, cross sections, or orientations. In an example, the spiralconductor portion 910B can instead be replaced with one or more otherconductor geometries, such as a serpentine conductor shown in theexample of FIG. 3B.

In the example of FIG. 9, one or more adjacent segments in the spiralconductor portion can be offset in depth from one another, such asdiscussed in the examples of FIGS. 5A-C. For example, such an offset indepth can help reduce an unwanted capacitive interaction betweenadjacent segments due at least in part to a fringing field effect.

FIGS. 10A-B illustrate generally an example of an apparatus 1000 thatcan include an implantable antenna 1010 that can include a spiralconductor. In the examples of FIGS. 10A-B, the spiral conductor can belocated within a dielectric compartment 1007 (e.g., a header of an IMD),such as in a region not otherwise occupied by or near a lead bore 1070or associated mechanical features (e.g., away from one or more contactsassociated with a lead connector assembly, or away from a set-screwassembly, etc.). In an example, such as shown in FIG. 10B, the antenna1010 can be shaped or formed so that a specified separation ismaintained between the antenna 1010 conductor, and a nearby conductorsuch as a housing of the IMD, such as shown near the region 1016. Such aconfiguration can provide less electrical loading of the antenna 1010 bythe housing 1005, as compared to an antenna including a portion as shownin the shaded regions 1017A-B.

FIGS. 11-18 generally show various illustrative examples of apparatuses1100, 1200, 1300, 1400, 1500, 1600, 1700, and 1800 that can include arespective implantable antenna 1110, 1210, 1310, 1410, 1510, 1610, 1710,or 1810 including a spiral conductor, the spiral conductor sized andshaped to provide specified electrical operating characteristics withina specified operating frequency range, the examples including variousdielectric compartment and housing configurations, such as included as aportion or part of an IMD.

In the examples of FIGS. 11-18, an IMD housing 1105, 1205, 1305, 1405,1505, 1605, 1705, or 1805 can include a conductive portion, such as ahermetically-sealed, laser-welded titanium enclosure, such as containingone or more circuit assemblies. Such circuit assemblies can include oneor more electrostimulation or physiologic sensing circuits, such ascoupled to one or more implantable lead assemblies via a connectorassembly 1170, 1270, 1370, 1470, 1570, 1670, 1770, or 1870, locatedwithin or as a portion of a dielectric compartment 1107, 1207, 1307,1407, 1507, 1607, 1707, or 1807. In the examples of FIGS. 1-18, variousdielectric compartment configurations can be used, such as determined byhow many implantable lead assemblies will be used (if any). Also, anumber of electrodes or a number of lead wires included in a respectivelead assembly can vary from one dielectric compartment 1107, 1207, 1307,1407, 1507, 1607, 1707, or 1807 to another. For example, a multi-polarlead connector can provide respective connections within the dielectriccompartment 1107, 1207, 1307, 1407, 1507, 1607, 1707, or 1807 torespective conductors connected to various electrical inputs or outputsof circuitry within the housing (e.g. via a hermetically-sealed filteredfeedthrough assembly). The present inventors have also recognized thatusing an antenna with a spiral conductor configuration “tucked” intootherwise unused space in the dielectric compartment 1107, 1207, 1307,1407, 1507, 1607, 1707, or 1807 may allow a common antenna design to beused across different dielectric compartment or housing configurations,such as reducing manufacturing complexity or increasing designflexibility.

In the examples of FIGS. 11-18, one or more physical parameters of thespiral conductor can be adjusted, such as to provide specifiedelectrical operating characteristics within a specified operatingfrequency range. As in the examples of FIGS. 5A-C, a number of turns ofthe spiral conductor, the lateral width of the spiral conductor, thesidewall height of the spiral conductor, a separation between adjacentturns of the spiral conductor, a path length along the spiral conductor,a total surface area of the antenna 1110, 1210, 1310, 1410, 1510, 1610,1710, or 1810, a diameter of a hypothetical sphere sized to enclose theantenna 110, 1210, 1310, 1410, 1510, 1610, 1710, or 1810, or aseparation between an end and an initial location along the antenna1110, 1210, 1310, 1410, 1510, 1610, 1710, or 1810 can affect variouselectrical characteristics of the antenna 1110, 1210, 1310, 1410, 1510,1610, 1710, or 1810. Such electrical characteristics can include a totalradiated power (TRP), a radiation an efficiency, a directivity, or aninput impedance, either in free space (e.g., air), or after implant intissue. For example, TRP can be determined with respect to a referencepower level, such as 1 milliwatt, and simulated or measured in decibel(e.g., logarithmic) units (e.g., dBm). Similarly, the directivity can bedetermined relative to an isotropic radiator, and simulated or measuredin decibel units (e.g., dBi).

The illustrative examples of FIGS. 11-18 can be simulated using anelectromagnetic modeling software package, such as Microwave Studio®,provided by Computer Simulation Technology, CST AG, Darmstadt, Germany.For example, TABLE 1, below, includes results of simulation performed onthe illustrative examples of FIGS. 11-18 to estimate various antenna1110, 1210, 1310, 1410, 1510, 1610, 1710, or 1810 electrical performancecharacteristics. Similarly, TABLE 2 illustrates generally variousantenna conductor dimensions corresponding to the various illustrativeexamples provided in TABLE 1.

TABLE 1 Antenna Simulation Results for Various Illustrative ExamplesImpedance - TRP - Directivity - Impedance - TRP - Directivity - Air AirAir in vivo in vivo in vivo Example (Ohms) (dBm) (dBi) (Ohms) (dBm)(dBi) FIG. 11 7 - j120 −27 1.9 25 - j30 −23 2.12 FIG. 12 7 - j135 −331.85 22 - j51 −27 2.25 FIG. 13 9 - j150 −36 1.85 22 - j66 −29 2.27 FIG.14 8.5 - j135  −28 1.87 26 - j41 −25 2.15 FIG. 15 9 - j147 −36 1.88 27 -j54 −28 2.4 FIG. 16 9 - j134 −35 1.89 27 - j42 −27 2.4 FIG. 17 8 - j135−33 1.88 23 - j37 −26 2.3 FIG. 18 9 - j140 −34 1.88 34 - j25 −25 2.3

TABLE 2 Antenna Conductor Dimensions Ribbon Spacing Total ribbon Width -between turns - length Example “w” (mils) “d” (mils) (inches) FIG. 11 5020 4.14 FIG. 12 50 20 3.25 FIG. 13 50 20 3.25 FIG. 14 45 15 4.8 FIG. 1534 15 4 FIG. 16 45 15 3.8 FIG. 17 45 20 3.8 FIG. 18 45 20 4.5

FIGS. 19A-B, 20A-B, 21A-B illustrate generally examples of an apparatus1900, 2000, or 2100, that can include an implantable antenna 1910B,2010B, or 2110B including a spiral conductor 1910A, 2010A, or 2110A, thespiral conductor sized and shaped to provide specified electricaloperating characteristics within a specified operating frequency range,the examples including various dielectric compartment and housingconfigurations. In the illustrative examples of FIGS. 19A-B, 20A-B, and21A-B, the spiral conductor 1910A, 2010A, or 2110A can be etched,stamped or otherwise formed (such as shown in the examples of FIGS. 7A-Cand elsewhere) to provide a substantially planar conductor, such asincluding a ribbon-shaped conductor cross section. A portion 1919, 2019,or 2119 of the spiral conductor 1910A, 2010A, or 2110A can be sized andshaped to provide an electrical attachment or bonding point, such as toallow an electrical coupling to be made between the antenna 1910B,2010B, or 2110B and circuitry within a housing 1905, 2005, or 2105 of anIMD.

In an example, the antenna 1910B, 2010B, or 2110B can be folded orotherwise formed into a desired configuration, such as located within adielectric compartment 1907, 2007, or 2107 away from one or moreelectrical connectors for one or more implantable lead assemblies, suchas a first lead bore 1970, 2070, or 2170. In an example, such as shownin FIGS. 19B, 20B, and 21B, the antenna 1910B, 2010B, or 2110B cansubstantially conform to the contour of one or more exterior faces ofthe dielectric compartment 1907, 2007, or 2107, such as to maintain aspecified depth within the compartment, or to maintain a specifiedseparation between the housing 1905, 2005, or 2105 and the antenna1910B, 2010B, or 2110B.

In the example of FIG. 20B, the antenna 2010B is spaced slightly furtheraway from the housing 2005 as compared to the example of FIG. 19B.Similarly, in the example of FIG. 21B, the antenna 2110B is spacedslightly further away from the lead connectors, such as the first leadbore 2170, as compared to the examples of FIGS. 19B and 20B. TABLE 3illustrates generally various antenna simulation results and physicaldimensions corresponding to the antennas 1910B, 2010B, and 2110B ofFIGS. 19B, 20B, and 21B. In the illustrative examples of FIGS. 20B-21B,the spacing between adjacent turns, “d,” can taper or vary along thepath of the antenna 2010B, or 2110B, thus a range of values are includedin TABLE 3.

TABLE 3 Antenna Simulation Results and Dimensions for VariousIllustrative Examples Spacing Ribbon between Total TRP - TRP - Width -turns - ribbon Overall Air in vivo “w” “d” length height Example (dBm)(dBm) (mils) (mils) (inches) (inches) FIG. 19B −34 −25 45 25 4.5141080.478 FIG. 20B −34 −26 45 12.5-15 4.460559 0.48 FIG. 21B −35 −28 4521.5-25 3.876241 0.483

FIG. 22 illustrates generally an example of technique 2200 that caninclude, at 2202, providing an implantable medical device including animplantable telemetry antenna, such as shown in one or more of theexamples of the previous figures. At 2204, the technique 2200 caninclude wirelessly transferring information electromagnetically usingthe implantable telemetry antenna, such as shown in the examples ofFIGS. 1-2, for an implantable antenna included as a portion of an IMD.

FIGS. 23A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly. In the example of FIG.23A, a dielectric core 2380 can be formed, such as injection moldedusing an epoxy or urethane compound. A portion of the dielectric core2380 can be insert-molded or otherwise formed to include one or moreset-screw blocks or other structures. For example, a spiral conductor2310 can form a portion of an antenna, such as discussed in the examplesabove. A portion of the dielectric core 2380 can be insert-molded orotherwise bonded to mechanically retain the spiral conductor 2310. Then,a dielectric compartment 2307 can be overmolded or otherwise formed tocontain the dielectric core 2380, and the spiral conductor 2310, such asto provide an implantable assembly. For example, the implantableassembly shown in FIG. 23B can include a header, such as to provide anelectrical or mechanical connection to one or more implantable leads,such as via a lead cavity or “bore” 2370. Such a header can then bemechanically attached to an implantable medical device housing, asdiscussed in the examples above. In the example of FIGS. 23A-B, thedielectric core can include two substantially parallel face portions,such as in the side-wall regions of the core 2380. The spiral conductorcan be conformed or otherwise shaped to extend along a portion of thetwo substantially parallel faces as shown in FIGS. 23A-B, and a centralportion of the spiral conductor 2310 can extend along a surface of thecore 2380, such as comprising a third face extending between the twoside-wall regions of the core 2380. Such a configuration provides a moreomni-directional antenna configuration while still efficiently using theavailable volume within the dielectric compartment 2307. In an example,the dielectric core 2380 can include a channel or one or more stakes,such as to retain or immobilize the spiral conductor 2310 prior, during,or after a molding operation or one or more other fabrication steps. Ina stake example, the spiral conductor 2310 can include a hole or one ormore other structures, and a stake can penetrate through or canotherwise retain the spiral conductor 2310, such as after the stake ispressed or deformed, using either acoustic energy, heat, or one or moreother techniques.

FIGS. 24A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly. In the example of FIG.24A, similar to the example of FIG. 23A, a dielectric core 2480 can beformed, such as injection molded or insert-molded to include one or moreset-screw blocks or other structures. Then, a dielectric compartment2407A can be overmolded or otherwise formed around the dielectric core.Unlike the example of FIGS. 23A-B, a module implantable antenna assemblycan be configured similarly to the examples of FIGS. 8A-C. For example,the dielectric compartment 2407A can include a cavity, a channel, or ageneral area where a dielectric shell 2407A can be attached. In anexample, the dielectric shell 2407A can be “U”-shaped, such as includingan exterior-facing portion, and an interior-facing portion. In theexample of FIG. 24A, the spiral conductor 2410 (such as a portion of animplantable antenna assembly) can be located on the interior-facingportion of the dielectric shell 2407A. In an example, the dielectricshell 2407A can be insert-molded around the spiral conductor 2410, suchas to retain the antenna 2410. Then, in the example of FIG. 24B,similarly to the examples of FIGS. 8A-C, the combination of thedielectric shell 2407A and the spiral conductor 2410 can be attached tothe dielectric compartment 2480, such as to immobilize the spiralconductor 2410. As in the examples above, the dielectric compartment canbe a header configured to provide an electrical or mechanical connectionto one or more implantable leads, such as via a lead bore 2470. As withall the examples discussed above and below, the dielectric compartment2480 need not be homogeneous or all-dielectric throughout its entirevolume. For example, in FIG. 24B, one or more set-screw blocks,connecting wires, or other structures can be included within thedielectric compartment. In an example, a portion of the dielectriccompartment 2480 can be hollow or can include a cavity or a channel.Such a cavity or a channel can initially be open, but can be laterfilled or overmolded with dielectric material such as an adhesive, aback-fill material, or one or more other materials, such as after makingone or more internal electrical or mechanical connections, or such asafter attachment of the dielectric shell 2407A to the dielectriccompartment 2480.

FIGS. 25A-B illustrate generally an example of an apparatus that caninclude a modular implantable antenna assembly. In FIG. 25A, adielectric core 2580 can be formed, such as molded or otherwisefabricated to include a cavity or channel. The cavity or channel can besized and shaped to complement a spiral conductor 2510, such as toretain or align the spiral conductor 2510. In an example, the core 2580can be insert-molded around a portion of the spiral conductor 2510. Inan example, the core can include a stake or other structure. Such astake or other structure can be used to attach the spiral conductor 2510to the core. In the example of FIG. 25B, a dielectric compartment 2507can contain the dielectric core 2580 and spiral conductor 2510. Forexample, the dielectric compartment 2507 can be formed by overmoldingthe dielectric core 2580, or by placing the antenna assembly comprisingthe core 2580 and spiral conductor 2510 into a cavity within thedielectric compartment 2507, and then backfilling any remaining space inthe cavity with medical adhesive or one or more other compounds. Thedielectric compartment 2507 can include one or more other structures,such as a set screw block or other mechanical or electrical connections,such as to provide an interface for an implantable lead via a leadconnector 2570.

In the examples of FIGS. 23A-B, 24A-B, and 25A-B, similar to theexamples of FIGS. 8A-C, a modular antenna assembly can be fabricated,such as tailored to a specific location of use (e.g., for use at aspecified range of frequencies, or for use with a particular model ofimplantable medical device). Such a modular assembly can allow anantenna configuration to be specified or selected for use with aspecified implantable medical device assembly (e.g., pairing aparticular antenna assembly to a desired implantable medical deviceconfiguration, such as during manufacturing). Also, such a modulardesign can allow revision to the antenna assembly, such as to the spiralconductor, without requiring the rest of the dielectric compartmentdesign to change, reducing the cost of development.

Various Examples

Example 1 includes subject matter (such as an apparatus) comprising animplantable medical device, including a housing, an implantabletelemetry circuit carried within the housing, a dielectric compartment,mechanically coupled to the housing, the dielectric compartmentincluding first and second substantially parallel face portions and athird face portion extending between the first and second face portion,an implantable telemetry antenna, located at least partially within thedielectric compartment. In Example 1, the implantable telemetry circuitis electrically coupled to the implantable telemetry antenna andconfigured to wirelessly transfer information electromagnetically usingthe implantable telemetry antenna, the implantable telemetry antennacomprises a spiral conductor portion extending along the first, second,and third face portions.

In Example 2, the subject matter of Example 1 can optionally include aspiral conductor comprising a planar spiral pattern including concentricturns, the planar spiral pattern folded so that respective portions ofthe planar spiral pattern are located near, and are substantiallyparallel to, the first and second face portions of the dielectriccompartment.

In Example 3, the subject matter of one or any combination of Examples1-2 can optionally include an implantable telemetry antenna comprising aloading portion, coupled to the spiral conductor and the implantabletelemetry circuit, the loading portion configured to adjust an inputimpedance of the implantable telemetry antenna, to provide a specifiedinput impedance range within a specified range of operating frequenciesto be used for wireless information transfer.

In Example 4, the subject matter of one or any combination of Examples1-3 can optionally include a loading portion comprising a conductivesegment substantially perpendicular to a surface of the housing, theconductive segment of the loading portion configured to adjust the inputimpedance of the implantable telemetry antenna by reducing or aboutcanceling a capacitive portion of the input impedance of the implantabletelemetry antenna.

In Example 5, the subject matter of one or any combination of Examples1-4 can optionally include a dielectric compartment of the implantablemedical device comprising a header configured to provide an electricaland mechanical connection to an implantable lead, the implantable leadincluding an electrode configured for location at a tissue site, andcoupled to electronic circuitry within the housing to provide one ormore of electrostimulation of tissue, or sensing of activity, at thesite of the electrode.

In Example 6, the subject matter of one or any combination of Examples1-5 can optionally include an implantable lead and the electrode.

In Example 7, the subject matter of one or any combination of Examples1-6 can optionally include a spiral conductor including a cross sectionhaving a lateral width that is greater than a sidewall height of thecross section.

In Example 8, the subject matter of one or any combination of Examples1-7 can optionally include a portion of the spiral conductor locatedtoward the housing and oriented so that the sidewall provides a facelocated near the housing that is substantially parallel to a surface ofthe housing.

In Example 9, the subject matter of one or any combination of Examples1-8 can optionally include a separation between adjacent turns of thespiral conductor decreased as compared to using a cross section lackingthe lateral width greater than the sidewall height to provide aspecified input impedance range within the specified range of operatingfrequencies.

In Example 10, the subject matter of one or any combination of Examples1-9 can optionally include a total surface area of the implantabletelemetry antenna increased as compared to using a cross section lackingthe lateral width greater than the sidewall height to provide aspecified input impedance range within the specified range of operatingfrequencies.

Example 11 includes subject matter (such as an apparatus) comprising animplantable medical device including a housing, an implantable telemetrycircuit carried within the housing, a dielectric compartment,mechanically coupled to the housing, an implantable telemetry antennalocated at least partially within the dielectric compartment, theimplantable telemetry circuit electrically coupled to the implantabletelemetry antenna and configured to wirelessly transfer informationelectromagnetically using the implantable telemetry antenna. In Example11, the implantable telemetry antenna comprises a spiral conductorextending along a face portion of the dielectric compartment, theconductor including a cross section having a lateral width that isgreater than a sidewall height of the cross section, and one or more ofa number of turns of the spiral conductor, the lateral width of thespiral conductor, the sidewall height of the spiral conductor, aseparation between adjacent turns of the spiral conductor, a path lengthalong the spiral conductor, a total surface area of the antenna, adiameter of a hypothetical sphere sized to enclose the antenna, or aseparation between an end and an initial location along the antenna, isused to provide a specified input impedance range, within a specifiedrange of operating frequencies to be used for wireless informationtransfer.

In Example 12, the subject matter of Example 11 can optionally include aseparation between adjacent turns of the spiral conductor decreased ascompared to using a cross section lacking the lateral width greater thanthe sidewall height to provide the specified input impedance rangewithin the specified range of operating frequencies.

In Example 13, the subject matter of one or any combination of Examples11-12 can optionally include a total surface area of the implantabletelemetry antenna increased as compared to using a cross section lackingthe lateral width greater than the sidewall height to provide thespecified input impedance range within the specified range of operatingfrequencies.

In Example 14, the subject matter of one or any combination of Examples11-13 can optionally include a spiral conductor comprising a planarspiral pattern including concentric turns, the planar spiral patternfolded so that at least a portion of the planar spiral pattern isparallel to the face portion of the dielectric compartment.

In Example 15, the subject matter of one or any combination of Examples11-14 can optionally include an implantable telemetry antenna includinga loading portion, coupled to the spiral conductor and the implantabletelemetry circuit, the loading portion configured to adjust an inputimpedance of the implantable telemetry antenna, to provide a specifiedinput impedance range within a specified range of operating frequenciesto be used for wireless information transfer.

In Example 16, the subject matter of one or any combination of Examples11-15 can optionally include a loading portion comprising a conductivesegment substantially perpendicular to a surface of the housing, theconductive segment of the loading portion configured to adjust the inputimpedance of the implantable telemetry antenna by reducing or aboutcanceling a capacitive portion of the input impedance of the implantabletelemetry antenna.

In Example 17, the subject matter of one or any combination of Examples11-16 can optionally include a dielectric compartment of the implantablemedical device comprising a header configured to provide an electricaland mechanical connection to an implantable lead, the implantable leadincluding an electrode configured for location at a tissue site, andcoupled to electronic circuitry within the housing to provide one ormore of electrostimulation of tissue, or sensing of activity, at thesite of the electrode.

In Example 18, the subject matter of one or any combination of Examples11-17 can optionally include an implantable lead and the electrode.

In Example 19, the subject matter of one or any combination of Examples11-18 can optionally include a portion of the spiral conductor locatedtoward the housing and is oriented so that the sidewall provides a facelocated near the housing that is substantially parallel to a surface ofthe housing.

Example 20 can include, or can optionally be combined with the subjectmatter of one or any combination of Examples 1-19 to include, subjectmatter (such as a method, a means for performing acts, or amachine-readable medium including instructions that, when performed bythe machine, cause the machine to perform acts) comprising providing animplantable medical device, including a dielectric compartment includingfirst and second substantially parallel face portions, and a third faceportion extending between the first and second face portions, animplantable telemetry antenna, located at least partially within thedielectric compartment, the implantable telemetry antenna comprising aspiral conductor portion extending along the first, second, and thirdface portions, and wirelessly transferring informationelectromagnetically using the implantable telemetry antenna.

Example 21 includes subject matter (such as an apparatus) comprising animplantable medical device including a housing, an implantable telemetrycircuit carried within the housing, a dielectric compartment,mechanically coupled to the housing, an implantable telemetry antenna,located at least partially within the dielectric compartment, theimplantable telemetry circuit electrically coupled to the implantabletelemetry antenna and configured to wirelessly transfer informationelectromagnetically using the implantable telemetry antenna. In Example21, the implantable telemetry antenna comprises a spiral conductorportion extending along a face portion of the dielectric compartment, aloading portion, coupled to the spiral conductor portion and theimplantable telemetry circuit, the loading portion comprising aconductive segment substantially perpendicular to a surface of thehousing, the conductive segment of the loading portion configured toadjust an input impedance of the implantable telemetry antenna, toprovide a specified input impedance range within a specified range ofoperating frequencies to be used for wireless information transfer.

In Example 22, the subject matter of Example 21 can optionally include aspiral conductor including a planar spiral pattern including concentricturns, the planar spiral pattern folded so that a portion of the planarspiral pattern is located near, and substantially parallel to, the faceportion of the dielectric compartment.

In Example 23, the subject matter of one or any combination of Examples21-22 can optionally include a dielectric compartment includes first andsecond substantially parallel face portions, and a third face portionextending between the first and second face portions, the implantabletelemetry antenna including a spiral conductor portion extending alongthe first, second, and third face portions.

In Example 24, the subject matter of one or any combination of Examples21-23 can optionally include a loading portion configured to adjust theinput impedance of the implantable telemetry antenna by adjusting orabout canceling a capacitive portion of the input impedance of theimplantable telemetry antenna.

In Example 25, the subject matter of one or any combination of Examples21-24 can optionally include a dielectric compartment of the implantablemedical device comprising a header configured to provide an electricaland mechanical connection to an implantable lead, the implantable leadincluding an electrode configured for location at a tissue site, andcoupled to electronic circuitry within the housing to provide one ormore of electrostimulation of tissue, or sensing of activity, at thesite of the electrode.

In Example 26, the subject matter of one or any combination of Examples21-25 can optionally include an implantable lead and the electrode.

In Example 27, the subject matter of one or any combination of Examples21-26 can optionally include a spiral conductor including a crosssection having a lateral width that is greater than a sidewall height ofthe cross section.

In Example 28, the subject matter of one or any combination of Examples21-27 can optionally include a portion of the spiral conductor locatedtoward the housing and is oriented so that the sidewall provides a facelocated near the housing that is substantially parallel to a surface ofthe housing.

In Example 29, the subject matter of one or any combination of Examples21-28 can optionally include a separation between adjacent turns of thespiral conductor decreased as compared to using a cross section lackingthe lateral width greater than the sidewall height to provide thespecified input impedance range within the specified range of operatingfrequencies.

In Example 30, the subject matter of one or any combination of Examples21-29 can optionally include a total surface area of the implantabletelemetry antenna increased as compared to using a cross section lackingthe lateral width greater than the sidewall height to provide thespecified input impedance range within the specified range of operatingfrequencies.

In Example 31, the subject matter of one or any combination of Examples21-30 can optionally include one or more of a number of turns of thespiral conductor, the lateral width of the spiral conductor, thesidewall height of the spiral conductor, a separation between adjacentturns of the spiral conductor, a path length along the spiral conductor,a total surface area of the antenna, a diameter of a hypothetical spheresized to enclose the antenna, or a separation between an end and aninitial location along the antenna, is used to provide the specifiedinput impedance range, within a specified range of operating frequenciesto be used for wireless information transfer.

In Example 32, the subject matter of one or any combination of Examples21-31 can optionally include a spiral conductor portion defining ahypothetical axis around which the spiral winds, the conductive spiralportion including a first winding that is offset in depth along thehypothetical axis from a second winding of the conductive spiral, andthe hypothetical axis substantially perpendicular to the face portion ofthe dielectric compartment, and a total depth of the spiral antenna,along the hypothetical axis, is at least an order of magnitude smallerthan a diameter or a largest linear dimension of a surface area enclosedby an outer-most turn of the spiral conductor.

In Example 33, the subject matter of one or any combination of Examples21-32 can optionally include a spiral conductor including one or more ofa tapered cross-sectional lateral width or a tapered spacing betweenadjacent turns, along the spiral conductor.

Example 34 includes subject matter (such as an apparatus) comprising animplantable medical device, including a housing, an implantabletelemetry circuit carried within the housing, a dielectric compartment,mechanically coupled to the housing, an implantable telemetry antenna,located at least partially within the dielectric compartment, theimplantable telemetry circuit electrically coupled to the implantabletelemetry antenna and configured to wirelessly transfer informationelectromagnetically using the implantable telemetry antenna, theimplantable telemetry antenna including a spiral conductor portionextending along a face portion of the dielectric compartment, the spiralconductor including one or more of a tapered cross-sectional lateralwidth or a tapered spacing between adjacent turns, along the spiralconductor, a loading portion, coupled to the spiral conductor portionand the implantable telemetry circuit, the loading portion comprising aconductive segment substantially perpendicular to a surface of thehousing, the conductive segment of the loading portion configured toadjust an input impedance of the implantable telemetry antenna, toprovide a specified input impedance range within a specified range ofoperating frequencies to be used for wireless information transfer.

Example 35 can include, or can optionally be combined with the subjectmatter of one or any combination of Examples 1-34 to include, subjectmatter (such as a method, a means for performing acts, or amachine-readable medium including instructions that, when performed bythe machine, cause the machine to perform acts) comprising providing animplantable medical device including a dielectric compartment includingfirst and second substantially parallel face portions, a third faceportion extending between the first and second face portions, and animplantable telemetry antenna, located at least partially within thedielectric compartment, the implantable telemetry antenna comprising aspiral conductor portion extending along a face portion of thedielectric compartment and a loading portion, coupled to the spiralconductor portion and the implantable telemetry circuit, the loadingportion comprising a conductive segment substantially perpendicular to asurface of the housing, the conductive segment of the loading portionconfigured to adjust an input impedance of the implantable telemetryantenna, to provide a specified input impedance range within a specifiedrange of operating frequencies to be used for wireless informationtransfer, and wirelessly transferring information electromagneticallyusing the implantable telemetry antenna.

In Example 36, the subject matter of Example 35 can optionally include aspiral conductor comprising a planar spiral pattern including concentricturns, the planar spiral pattern folded so that a portion of the planarspiral pattern is located near, and substantially parallel to, the faceportion of the dielectric compartment.

In Example 37, the subject matter of one or any combination of Examples35-36 can optionally include a dielectric compartment comprising firstand second substantially parallel face portions, and a third faceportion extending between the first and second face portions, and theimplantable telemetry antenna comprising a spiral conductor portionextending along the first, second, and third face portions.

In Example 38, the subject matter of one or any combination of Examples35-37 can optionally include adjusting the input impedance of theimplantable telemetry antenna by adjusting or about canceling acapacitive portion of the input impedance of the implantable telemetryantenna.

In Example 39, the subject matter of one or any combination of Examples35-38 can optionally include a spiral conductor comprising a crosssection having a lateral width that is greater than a sidewall height ofthe cross section, and adjusting the input impedance of the implantabletelemetry antenna using one or more of a number of turns of the spiralconductor, the lateral width of the spiral conductor, the sidewallheight of the spiral conductor, a separation between adjacent turns ofthe spiral conductor, a path length along the spiral conductor, a totalsurface area of the antenna, a diameter of a hypothetical sphere sizedto enclose the antenna, or a separation between an end and an initiallocation along the antenna, to provide a specified input impedancerange, within a specified range of operating frequencies to be used forwireless information transfer.

In Example 40, the subject matter of one or any combination of Examples35-39 can optionally include a spiral conductor comprising one or moreof a tapered cross-sectional lateral width or a tapered spacing betweenadjacent turns, along the spiral conductor.

Example 41 includes subject matter (such as an apparatus) comprising animplantable antenna assembly, including a dielectric shell includingfirst and second substantially parallel outer face portions, and a thirdouter face portion extending between the first and second portions, aspiral conductor extending along the first, second, and third portionson a surface of the dielectric shell, the dielectric shell and spiralconductor configured to be mechanically attached to a dielectriccompartment configured to be coupled to a housing of an implantablemedical device, the implantable antenna assembly configured to beelectrically coupled to an implantable telemetry circuit configured towirelessly transfer information electromagnetically using theimplantable telemetry antenna.

In Example 42, the subject matter of Example 41 can optionally include aspiral conductor configured to extend along an interior-facing surfaceof the dielectric shell.

In Example 43, the subject matter of one or any combination of Examples41-42 can optionally include a spiral conductor configured to extendalong an exterior-facing surface of the dielectric shell.

In Example 44, the subject matter of one or any combination of Examples41-43 can optionally include a dielectric shell and spiral conductorconfigured to be contained at least partially within the dielectriccompartment by a material comprising at least a portion of thedielectric compartment.

In Example 45, the subject matter of one or any combination of Examples41-44 can optionally include a dielectric shell configured tomechanically retain the spiral conductor, using at least one of a stakeor a channel.

In Example 46, the subject matter of one or any combination of Examples41-45 can optionally include a stake configured to retain a portion ofthe spiral conductor when the stake is deformed.

In Example 47, the subject matter of one or any combination of Examples41-46 can optionally include a dielectric shell configured tomechanically immobilize the spiral conductor when the dielectric shellis molded around at least a portion of the spiral conductor.

In Example 48, the subject matter of one or any combination of Examples41-47 can optionally include one or more of the dielectric shell or thespiral conductor adhesively attached to the dielectric compartment.

In Example 49, the subject matter of one or any combination of Examples41-48 can optionally include an implantable medical device including thehousing, the dielectric compartment, mechanically coupled to the housingand mechanically coupled to the implantable antenna assembly, theimplantable telemetry circuit carried within the housing and configuredto wirelessly transfer information electromagnetically using theimplantable antenna assembly.

In Example 50, the subject matter of one or any combination of Examples41-49 can optionally include a dielectric compartment of the implantablemedical device comprising a header configured to provide an electricaland mechanical connection to an implantable lead, the implantable leadincluding an electrode configured for location at a tissue site, andcoupled to electronic circuitry within the housing to provide one ormore of electrostimulation of tissue, or sensing of activity, at thesite of the electrode.

In Example 51, the subject matter of one or any combination of Examples41-50 can optionally include an implantable lead and the electrode.

Example 52 includes subject matter (such as an apparatus) comprising animplantable antenna assembly, comprising a dielectric core includingfirst and second substantially parallel face portions, and a third faceportion extending between the first and second portions, a cavity sizedand shaped to accept an implantable lead connector, a spiral conductorextending along the first, second, and third portions on an exteriorsurface of the dielectric core, the dielectric core and spiral conductorare configured to be at least partially contained within a dielectriccompartment, and the implantable antenna assembly configured to beelectrically coupled to an implantable telemetry circuit configured towirelessly transfer information electromagnetically using theimplantable telemetry antenna.

In Example 53, the subject matter of Example 52 can optionally include adielectric core configured to mechanically retain the spiral conductor,using at least one of a stake or a channel.

In Example 54, the subject matter of one or any combination of Examples52-53 can optionally include a dielectric core configured tomechanically immobilize the spiral conductor when the dielectric core ismolded around at least a portion of the spiral conductor.

In Example 55, the subject matter of one or any combination of Examples52-54 can optionally include an implantable medical device including thehousing, the dielectric compartment, mechanically coupled to the housingand mechanically coupled to the implantable antenna assembly, and theimplantable telemetry circuit carried within the housing and configuredto wirelessly transfer information electromagnetically using theimplantable antenna assembly.

In Example 56, the subject matter of one or any combination of Examples52-55 can optionally include a combination of the dielectric compartmentand the dielectric core comprising a header configured to provide anelectrical and mechanical connection to an implantable lead, theimplantable lead including an electrode configured for location at atissue site and coupled to electronic circuitry within the housing toprovide one or more of electrostimulation of tissue, or sensing ofactivity, at the site of the electrode.

In Example 57, the subject matter of one or any combination of Examples52-56 can optionally include an implantable lead and the electrode.

Example 58 can include, or can optionally be combined with the subjectmatter of one or any combination of Examples 1-57 to include, subjectmatter (such as a method, a means for performing acts, or amachine-readable medium including instructions that, when performed bythe machine, cause the machine to perform acts) comprising attaching aspiral conductor to a dielectric shell, the dielectric shell includingfirst and second substantially parallel outer face portions, and a thirdouter face portion extending between the first and second portions, thespiral conductor configured to extend along the first, second, and thirdportions on a surface of the dielectric shell, and mechanically couplingthe dielectric shell and the spiral conductor to a dielectriccompartment configured to be coupled to a housing of an implantablemedical device.

In Example 59, the subject matter of Example 58 can optionally includemechanically coupling the dielectric shell and spiral conductor to thedielectric compartment including overmolding the dielectric shell andspiral conductor using a material comprising at least a portion of thedielectric compartment.

In Example 60, the subject matter of one or any combination of Examples58-59 can optionally include mechanically coupling the dielectric shelland spiral conductor to the dielectric compartment including adhesivelycoupling the dielectric shell or the spiral conductor to the dielectriccompartment.

ADDITIONAL NOTES

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

All publications, patents, and patent documents referred to in thisdocument are incorporated by reference herein in their entirety, asthough individually incorporated by reference. In the event ofinconsistent usages between this document and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, or process that includes elements in addition to those listedafter such a term in a claim are still deemed to fall within the scopeof that claim. Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

Method examples described herein can be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, the code can be tangibly stored on one ormore volatile or non-volatile tangible computer-readable media, such asduring execution or at other times. Examples of these tangiblecomputer-readable media can include, but are not limited to, hard disks,removable magnetic disks, removable optical disks (e.g., compact disksand digital video disks), magnetic cassettes, memory cards or sticks,random access memories (RAMs), read only memories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment, and it is contemplated that such embodiments can be combinedwith each other in various combinations or permutations. The scope ofthe invention should be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

The claimed invention is:
 1. An apparatus, comprising: an implantablemedical device comprising: a housing; an implantable telemetry circuitcarried within the housing; a dielectric compartment, mechanicallycoupled to the housing, the dielectric compartment including first andsecond substantially parallel face portions, and a third face portionextending between the first and second face portions; an implantabletelemetry antenna, located at least partially within the dielectriccompartment; wherein the implantable telemetry circuit is electricallycoupled to the implantable telemetry antenna and configured towirelessly transfer information electromagnetically using theimplantable telemetry antenna; and wherein the implantable telemetryantenna comprises: a spiral conductor extending along and substantiallyconforming to the contours of the first, second, and third face portionsof the dielectric compartment, wherein the spiral conductor comprises aplanar spiral pattern including concentric turns; and a loading portion,coupled to the spiral conductor and the implantable telemetry circuit,the loading portion comprising a conductive segment substantiallyperpendicular to a surface of the housing, the conductive segment of theloading portion configured to adjust an input impedance of theimplantable telemetry antenna, to provide a specified input impedancerange within a specified range of operating frequencies to be used forwireless information transfer.
 2. The apparatus of claim 1, wherein theplanar spiral pattern is folded so that a portion of the planar spiralpattern is located near, and substantially parallel to, the third faceportion of the dielectric compartment.
 3. The apparatus of claim 1,wherein the loading portion is configured to adjust the input impedanceof the implantable telemetry antenna by adjusting or about canceling acapacitive portion of the input impedance of the implantable telemetryantenna.
 4. The apparatus of claim 1, wherein the dielectric compartmentof the implantable medical device comprises a header configured toprovide an electrical and mechanical connection to an implantable lead,the implantable lead including an electrode configured for location at atissue site, and coupled to electronic circuitry within the housing toprovide one or more of electrostimulation of tissue, or sensing ofactivity, at the site of the electrode.
 5. The apparatus of claim 4,further comprising the implantable lead and the electrode.
 6. Theapparatus of claim 1, wherein the spiral conductor includes a crosssection having a lateral width that is greater than a sidewall height ofthe cross section.
 7. The apparatus of claim 6, wherein a portion of thespiral conductor is located toward the housing and is oriented so thatthe sidewall provides a face located near the housing that issubstantially parallel to a surface of the housing.
 8. The apparatus ofclaim 6, wherein the separation between adjacent turns of the spiralconductor is decreased as compared to using a cross section lacking thelateral width greater than the sidewall height to provide the specifiedinput impedance range within the specified range of operatingfrequencies.
 9. The apparatus of claim 6, wherein the total surface areaof the implantable telemetry antenna is increased as compared to using across section lacking the lateral width greater than the sidewall heightto provide the specified input impedance range within the specifiedrange of operating frequencies.
 10. The apparatus of claim 6, whereinone or more of a number of turns of the spiral conductor, the lateralwidth of the spiral conductor, the sidewall height of the spiralconductor, a separation between adjacent turns of the spiral conductor,a path length along the spiral conductor, a total surface area of theantenna, a diameter of a hypothetical sphere sized to enclose theantenna, or a separation between an end and an initial location alongthe antenna, is used to provide the specified input impedance range,within a specified range of operating frequencies to be used forwireless information transfer.
 11. The apparatus of claim 1, wherein thespiral conductor portion defines a hypothetical axis around which thespiral winds, the conductive spiral portion including a first windingthat is offset in depth along the hypothetical axis from a secondwinding of the conductive spiral, and the hypothetical axissubstantially perpendicular to the face portion of the dielectriccompartment; and wherein a total depth of the spiral antenna, along thehypothetical axis, is at least an order of magnitude smaller than adiameter or a largest linear dimension of a surface area enclosed by anouter-most turn of the spiral conductor.
 12. The apparatus of claim 1,wherein the spiral conductor includes one or more of a taperedcross-sectional lateral width or a tapered spacing between adjacentturns, along the spiral conductor.
 13. An apparatus, comprising: animplantable medical device comprising: a housing; a dielectriccompartment, mechanically coupled to the housing, the dielectriccompartment including first and second substantially parallel faceportions, and a third face portion extending between the first andsecond face portions; an implantable telemetry circuit carried withinthe housing; an implantable telemetry antenna, located at leastpartially within the dielectric compartment; wherein the implantabletelemetry circuit is electrically coupled to the implantable telemetryantenna and configured to wirelessly transfer informationelectromagnetically using the implantable telemetry antenna; and whereinthe implantable telemetry antenna comprises: a spiral conductorextending along and substantially conforming to the contours of thefirst, second, and third face portions of the dielectric compartment,the spiral conductor including one or more of a tapered cross-sectionallateral width or a tapered spacing between adjacent turns, along thespiral conductor, wherein the spiral conductor comprises a planar spiralpattern including concentric turns; and a loading portion, coupled tothe spiral conductor portion and the implantable telemetry circuit, theloading portion comprising a conductive segment substantiallyperpendicular to a surface of the housing, the conductive segment of theloading portion configured to adjust an input impedance of theimplantable telemetry antenna, to provide a specified input impedancerange within a specified range of operating frequencies to be used forwireless information transfer.
 14. A method, comprising: providing animplantable medical device comprising: a dielectric compartmentincluding first and second substantially parallel face portions, and athird face portion extending between the first and second face portions;and an implantable telemetry antenna, located at least partially withinthe dielectric compartment, the implantable telemetry antennacomprising: a spiral conductor portion extending along and substantiallyconforming to the contours of the first, second, and third face portionsof the dielectric compartment, wherein the spiral conductor comprises aplanar spiral pattern including concentric turns; and a loading portion,coupled to the spiral conductor portion and the implantable telemetrycircuit, the loading portion comprising a conductive segmentsubstantially perpendicular to a surface of the housing, the conductivesegment of the loading portion configured to adjust an input impedanceof the implantable telemetry antenna, to provide a specified inputimpedance range within a specified range of operating frequencies to beused for wireless information transfer; and wirelessly transferringinformation electromagnetically using the implantable telemetry antenna.15. The method of claim 14, wherein the planar spiral pattern is foldedso that a portion of the planar spiral pattern is located near, andsubstantially parallel to, the third face portion of the dielectriccompartment.
 16. The method of claim 14, comprising adjusting the inputimpedance of the implantable telemetry antenna by adjusting or aboutcanceling a capacitive portion of the input impedance of the implantabletelemetry antenna.
 17. The method of claim 14, wherein the spiralconductor includes a cross section having a lateral width that isgreater than a sidewall height of the cross section; and wherein themethod comprises adjusting the input impedance of the implantabletelemetry antenna using one or more of a number of turns of the spiralconductor, the lateral width of the spiral conductor, the sidewallheight of the spiral conductor, a separation between adjacent turns ofthe spiral conductor, a path length along the spiral conductor, a totalsurface area of the antenna, a diameter of a hypothetical sphere sizedto enclose the antenna, or a separation between an end and an initiallocation along the antenna, to provide a specified input impedancerange, within a specified range of operating frequencies to be used forwireless information transfer.
 18. The method of claim 14, wherein thespiral conductor includes one or more of a tapered cross-sectionallateral width or a tapered spacing between adjacent turns, along thespiral conductor.